Prior Art air traffic control systems are geared up to track planes in the air and on runway surface areas to optimize efficiency and provide safety. Safety is assured by “separation” whereby air traffic controllers employ various procedures and technologies to make sure that aircraft are physically separated by a minimum distance. At most airports, the responsibility of air traffic control starts and stops at the entrance or exit to the runway movement areas, which are taxiways and runways.
This is a practical matter, and in the non-movement areas, such as hangers, ramps, and aprons, aircraft movements and separation are no longer the responsibility of air traffic control, but is the responsibility of other parties such as the airport itself, airlines, or other parties. The use of tracking technologies for air traffic control is therefore focused on the movement areas, not the non-movement areas, where there are limitations in aircraft tracking. Furthermore, many of the aircraft transmitting devices are switched off in non-movement areas exacerbating tracking problems in these areas.
Airport airside operations are conducted on movement areas and non-movement areas. Movement areas refer to the airport's runways and taxiways and non-movement areas refer to the aprons, ramps, maintenance facilities, de icing facilities and other areas. One of the main differences between movement and non-movement areas is that usually Air Traffic Control (ATC) is responsible for separation and safety of aircraft in the movement areas, whereas the airport or other organization is responsible for operations in the non-movement areas. This is exemplified at a typical airport where the airport's ramp management will authorize an aircraft for push back, and the aircraft will taxi to a point at the edge of the controlled movement area, and the pilot will then contact ATC by radio to request clearance to proceed into the movement area for departure.
Movement and non-movement areas are described the RNP report Development of Airport Surface Required Navigation Performance (RNP), by Rick Cassell, Alex Smith, and Dan Hicok, Rannoch Corporation, Alexandria, Va. (NASA/CR-1999-209109, National Aeronautics and Space Administration, Langley Research Center, Hampton, Va. 23681-2199, Prepared for Langley Research Center under Contract NAS1-19214), incorporated herein by reference. FIG. 1 is taken from the Cassell et al., reference and illustrates, in a simplified form, the airport movement areas, and, enclosed within dashed lines, the non-movement areas.
Since Air Traffic Control (ATC) is responsible for the movement areas, the air traffic control infrastructure is optimized to provide communications, navigation, and surveillance in the movement areas, not the non-movement areas. Therefore at a typical larger airport there exists aircraft tracking and identification systems providing generally good coverage over the movement parts of an airport, but generally not throughout the non-movement areas.
The technologies that are currently used at airports for tracking in the movement areas are classified as cooperative, primary active, and passive. Cooperative technologies interact with devices on the aircraft, primary active technologies do not interact but use a form of transmission to reflect signals from aircraft, and passive technologies are receive only. Passive can include reception of any electromagnetic, radio, or radar transmission from an aircraft including, but not limited to those for communication, navigation, and surveillance, including signals that may be reflected from the aircraft.
Cooperative technologies include transponder-based systems such as ADS-B and multilateration as described in the following papers, all of which are incorporated herein by reference.                Analysis of ADS-B, ASDE-3 and Multilateration Surveillance Performance—NASA Atlanta Demonstration Presented at the AIAA 17th Annual Digital Avionics Systems Conference in October, 1998.        Application of ADS-B for Airport Surface Surveillance, AIAA 17th Annual Digital Avionics Systems Conference, October 1998.        Surveillance Monitoring of parallel Precision Approaches in a Free Flight Environment, AIAA 16th Annual Digital Avionics Systems Conference, October 1997.        Evaluation of Airport Surface Surveillance Technologies, IEEE Radar 96 conference, Beijing, China, October 1996. This paper reviews the evolving requirements for airport surveillance systems, particularly the use of the Required Surveillance Performance (RSP) concept.        Positive Identification of Aircraft on Surface Movement Area—Results of FAA Trials, 10th Annual International AeroSense Symposium, Orlando, Fla., April 1996        Atlanta Hartsfield International Airport—Results of FAA Trials to Accurately Locate/Identify Aircraft on the Airport Movement Area, IEEE PLANS, Atlanta, Ga., April 1996.        Improved Location/Identification of Aircraft/Ground Vehicles on Airport Movement Areas—Results of FAA Trials, Institute of Navigation in Santa Monica, Calif., January 1996.        
In 2000, in the United States, the FAA awarded a contract to Sensis for a surface multilateration system under the program name of ASDE X. The Airport Surface Detection Equipment-Model X (ASDE-X) program was initiated in 1999 and Sensis Corporation was selected as the vendor in the year 2000. The Senate Committee on Appropriations, in its report on FAA's fiscal year (FY) 2006 appropriations, expressed concern about the pace of ASDE-X deployment and reported the FAA has not yet deployed systems to more than half of the planned sites due to changes in system design and additional requirements.
The FAA originally planned to complete ASDE-X deployment to second-tier airports (e.g., Orlando International Airport and Milwaukee General Mitchell International Airport) by FY 2007 as a low-cost alternative to Airport Surface Detection Equipment-3 (ASDE-3) radar systems, which are deployed at larger, high-volume airports. However, the FAA now plans to complete deployment by FY 2009, a two-year delay. While the FAA has already procured 36 out of 38 ASDE-X systems, only 3 systems have been commissioned for operational use as of late 2005. As of 2005, the FAA has invested about $250 million in ASDE-X and expects to spend a total of $505 million to complete the program. A map of planned ASDE-X installations (from www.asdex.net, see http://www.sensis.com/docs/128/) as well as upgrades to the older ASDE-3 systems is illustrated in FIG. 2.
Primary technologies include Radar systems such as X-Band radar (see www.terma.com, incorporated herein by reference), as well as millimeter wave radar (see www.flight-refuelling.com, www.qinetic.com, and www.transtech-solutions.com, incorporated herein by reference). Some companies also use a combination of active sensors for detecting items on airport surfaces, for example debris. Roke Manor has a mobile system as detailed in U.S. patent application Ser. No. 10/494,271, Publication No. 20050046569, entitled “Detection of undesired objects on surfaces” published Mar. 3, 2005 and incorporated herein by reference. Qinetiq has an active system slated for Vancouver Airport to detect runway debris (See, www.qinetic.com, incorporated herein by reference).
Passive technologies include inductive loops buried in the surface as well as camera technology, both of which are described in the following papers, both of which are incorporated herein by reference:                Inductive Loop Sensor Subsystem (LSS) as a Supplemental Surface Surveillance System —Demonstration Results, AIAA 19th Annual Digital Avionics Systems Conference, October 2000.        Evaluation of FLIR/IR Camera Technology for Airport Surface Surveillance, 10th Annual International AeroSense Symposium in Orlando, Fla., April 1996.        
Existing techniques for runway occupancy determination include the use of zones as described in U.S. Pat. No. 6,927,701, entitled “Runway occupancy monitoring and warning,” issued Aug. 9, 2005, and incorporated herein by reference. Techniques for passive tracking using “bounced” signals include Roke Manor's triangulation techniques as described in U.S. Pat. No. 6,930,638, entitled “Passive moving object detection system and method using signals transmitted by a mobile telephone station,” issued Aug. 16, 2005, and also incorporated herein by reference.
Given the delays in the rollout of the ASDE-X program, as well as questions as to its operability, other techniques may be required to insure that aircraft can be accurately tracked throughout an airport, in movement and non-movement areas. Collisions between aircraft and other aircraft, service vehicles, buildings, or the like, can have devastating consequences, even at taxiing speeds. Moreover, even minor damage caused by such collisions may require expensive repairs and delay flights considerably. A system is needed which can accurately track aircraft in both movement and non-movement areas, which does not necessarily rely upon a single signal or technology. Such a system should be robust, redundant, inexpensive, and easy to install.
Cell phones, PDAs and other personal communication devices may soon have no limits on their use on airplanes. If regulations allow, cell phones and other radio devices may be approved for in-flight use during most or all phases of flight. If this use is allowed, then an additional set of radio signals may be emitting from an aircraft. In addition, some phones have added a GPS chip to aid in determining their locations and for compliance with the enhanced 911 requirements.
Air France is slated to trial OnAir passenger mobile phone use. Air France will take delivery of an A318 fitted with OnAir equipment in early 2007 that will enable the use of passenger mobile phones in-flight. The airline will then use the aircraft to conduct a six-month commercial trial using the new service on short-haul flights within Europe and to and from North Africa.
The OnAir service will allow Air France passengers to use their own GSM (global system for mobile communications) phones and GPRS (general packet radio service)-enabled devices such as the Blackberry or Treo, to make and receive voice calls or to send and receive SMS (short message service) communications, or emails during the flight, without inferring with critical aircraft systems.